With sharp edges designed for cutting, knives inherently present a danger of inadvertent cutting. This danger is particularly prevalent with utility knives where rapid and repeated cutting operations often are demanded. In such instances, the demanded speed or the monotony of repeated cutting operations may lead to a worker's not exercising a sufficient degree of care to maintain his or her own safety. For example, such a hurried or bored worker may use one hand to slice the razor blade quickly through a cardboard box or another article to be sliced, past the edge of the article, and into painful engagement with the worker's other hand, leg, or other body part Other problems often arise when a user employs a utility knife to perform a cutting operation and forgets to retract the device's razor blade. With this, a user swinging his or her arms while walking could inflict a painful gash to his or her own leg or to the body of another. Certainly, numerous other potential dangers resulting from an exposed razor blade will be obvious.
For many years, it was generally accepted that the dangers presented by utility knives were unavoidable. Advantageously, however, a plurality of inventors have made numerous attempts at making utility knives safer for normal use while compromising the knives' utility as little as possible. For example, the prior art reveals a utility knife with a pivotable, spring-biased guard that rotates from a blade-shielding position for protecting a user from the dangers of the razor blade to a blade-exposing position for allowing the performance of a cutting operation. Another utility knife provides an elongate safety guard that is disposed immediately adjacent to the cutting edge of the razor blade. The safety guard is longitudinally reciprocatable and is biased to an extended position such that it can retract to expose the razor blade to allow cutting and it can extend to shield the razor blade immediately after the utility knife is removed from the article being cut.
Unfortunately and notwithstanding the useful efforts of such previous inventors, utility knives continue to suffer from a plurality of disadvantages. For example, retractable blade shields in prior art devices normally shield both sides of a razor blade. With such shields, a user certainly enjoys some protection from the razor blade. However, the blade shield disadvantageously blocks the razor blade from a users sight. As a result, a user can forget or not notice that the razor blade is in an extended position whereby the very protection sought in providing the blade shield acts to endanger a user who might put the utility knife in the user's pocket or otherwise expose the user to danger from the unseen blade.
It must be recognized that utility knives have been disclosed with a blade shield disposed only on one side of a retained razor blade. These devices advantageously allow a user to view a retained razor blade even while the blade shield is in position protecting the user from the razor blade. However, such blade shields are known to be fixed relative to their respective utility knives. As a result, cutting with such utility knives requires that the razor blade be extended to a position beyond the blade shield or cutting operations with such a utility knife must be limited or specially adapted.
On a different note, one skilled in the art will be aware that in the most basic of utility knives, which is commonly referred to as a box cutter, replacing a razor blade comprises the relatively simple task of sliding a blade retainer from within a sheath, removing the dulled or broken blade from the blade retainer, inserting a blade with a sharp edge into the blade retainer, and sliding the blade retainer again into the sheath. Unfortunately, these box cutter utility knives can be among the most dangerous of utility knives. Not only is the razor blade completely unshielded when extended, but also the blade retainer is unrestrictedly slidable relative to the sheath whereby the razor blade can be extended unintentionally to present a most dangerous surprise.
Later-developed utility knives, for example those with shields or locking mechanisms, seek to cure one or more of the box cutter's drawbacks. In doing so, however, such knives have made it difficult or even impossible to replace spent razor blades. In many knives, a separate tool, such as a screwdriver, is required. Other knives are designed to be disposable, and they provide no means of replacing a spent razor blade. Such disposable knives often have elongate blades that are scored to allow a user to snap off distal sections of the blade when they become dull thereby to present a new, sharp section. Unfortunately, snapping sections from the blades of such knives presents a further danger from flying shards of worn metal.
In light of the foregoing, it becomes clear that a utility knife presenting a solution to one or more of the aforementioned deficiencies left by the prior art would be useful. However, it is dearer still that a utility knife presenting a solution to each and every one of the aforementioned problems while providing a number of heretofore unrealized advantages would represent a marked advance in the art.